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Lookup NU author(s): Professor Andrew Benniston,
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By using the unique fluorescence rejection method of Kerr-gating, detailed picosecond time-resolved resonance Raman experiments have been performed on the highly fluorescent photodynamic therapy dye, Merocyanine 540 (MC540). This has enabled collection of the first-singlet trans excited resonance Raman spectra of this dye in a range of protic and aprotic solvents of varying viscosity and polarity, as well as an organized reverse micelle. The detailed vibrational spectra support the idea that protic solvents form a H-bonded cluster around the oxygen groups of the thiobarbiturate group, which lock the group in position and hinder its rotation. In the reverse micelle containing hexane/AOT and a water pool (ωo = 32) the dye is orientated to permit the thiobarbiturate group to interact with water pool molecules. Using the Kerr-gate setup, time-resolved emission spectra of MC540 were also recorded in various solvents. The dye undergoes fast vibrational cooling (2-10 ps), which can be related to the solvent's thermal diffusivity. A second slower process (20-100 ps) also occurs, which is viscosity dependent and is associated with structural relaxation of the polymethine unit within the dye.
Author(s): Benniston AC, Matousek P, McCulloch IE, Parker AW, Towrie M
Publication type: Article
Publication status: Published
Journal: Journal of Physical Chemistry A
ISSN (print): 1089-5639
ISSN (electronic): 1520-5215
Publisher: American Chemical Society
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